Method of producing combustible gas rich in oil gas



-March 25, 1958 c. B. GLOVER ET AL MTHOD OF' PRODUCING COMBUSTIBLE GASRICH IN OIL GAS Filed April 3o, 1954 l l//ll/ //////u/// /////l /l l,/f/ /uf//// 1/ /l///////// /lM/l Ymae 670W.

United States Patent METHOD OF PRODUCING COMBUSTIBLE GAS RICH IN OIL GASApplication April 30, 1954, Serial No. 426,776

6 Claims. (Cl. 48-214) The present invention relates to a novel methodfor producing a combustible gas; and, more particularly, it relates to amethod for making a combustible gas rich in high B. t. u. oil gas by acyclic procedure involving a nickel catalyst and resulting in gas-makingeiciencies substantially higher than those realized in the oil gasprocesses heretofore practiced.

The manufacture of oil gas by the pyrolysis of oil is well known. Thegeneral procedure involves a cycle in one portion of which a mass ofheat storage' refractory material, usually in the form of checkerwork,is heated by passing hot combustion products in contact therewith,

and, in another portion of which, vaporized oil is py-v rolyzed, thatis, thermally cracked, into a fixed gas in passing through the heatedrefractory material. Oil gas made in this manner consists essentially ofgaseous hydrocarbons and hydrogen. When process steam is employed, as isusually Vthe case, it may react with carbon deposited during the processto produce water gas (carbon monoxide plus hydrogen). The amount ofwater gas present in the oil gas is generally very minor. The severityof the thermal cracking determines the heating value ofthe oil gas, themore severe the Acracking the lower the percentage of higher hydrocarbongases and the higher the percentage of hydrogen in the gas and thegreater-the amount of carbon formed. In conventional practice, true oil'gas values of less than 1000 B. t. u. can not be made thermally withoutexcessive carbon formation. To the extent that this carbon is convertedby process steam vto water gas, the heating value of the resulting mixedgas is further reduced.

In the purely thermal cracking of oil molecules, hydrocarbon fragmentscontaining lesser numbers of carbon atoms together with free hydrogenand carbon are rst formed. The hydrocarbon fragments, or free radicals,rearrange themselves in part to the thermally more stable hydrocarbongases such as methane, ethylene, propylene, and the like, and in part tomore stable aromatic ring compounds. These compounds, in turn, aresubject to fragmentation or recracking at higher temperatures or longertimes of contact, with the productionof more free hydrogen and more freecarbon and solid aromatic hydrocarbons. When steam is employed, some ofthe deposited carbon, as statedmay react therewith forming, by the watergas reaction, hydrogen and carbon monoxide. In commercial oil gasoperations, a balance of temperature and contact time is selected bywhich the ratio of the normally gaseous hydrocarbons relative tocondensibles, aromatics, pitch and carbon, is as high as practicable forthe feed stocks employed and for the B. t. u. levels desired in the gas.These ratios in conventional checkerwork oil gas sets are of the orderof 40 to 50% for petroleum oils of lowy Conradson carbon presentsproblems with the respect to thev elimination thereof since its presencein the gas serves as a contaminant while its accumulation in the heatstorage refractory material may result inr clogging of the intersticesthereof. The production of tar and other liquid products requiresexpensive equipment for removing'such materials fromY the finished gas.This latter requirement represents an economic disadvantage where theproduction of the oil gas is primarily to serve peak load demands inwhich case low equipment cost is the primary consideration.

It isalso known that hydrocarbons can be completely reacted with steamin the presence of nickel to form a gas consisting essentially ofhydrogen and oxides of carbon, mainly carbon monoxide. The hydrocarbonsmost generally used .in this reforming procedure are the gaseoushydrocarbons, particularly methane, although, in certain circumstances,liquid hydrocarbons may be used. The resulting gaseous product,consisting essentially of hydrogen `and carbon monoxide as thecombustibles, possesses a relatively low heatingl value, normally in theneighborhoodrof Z50-350 B. t. u. per cubic foot, and thereforerequiresjenrichinent with a gas of higher heating value, such asjnaturalgas or oil gas, in order to provide the desiredlheating value, beforedistribution in city gas mains. A

There have been suggestions concerning the possibility of partiallyVreforming hydrocarbons catalytically into a combustible gas containingsome gaseous hydrocarbons and having a higherV heating value than thecompletely reformed gas referred to in the preceding paragraph. With onepossible exception, however, applicants know of no actual instance whereliquid hydrocarbons have` been converted into a combustible gas rich inoil gas and having a heating value in the high B. t. u. oil gas rangethrough the agency of a nickel catalyst. The possible exception referredto is a process recently developed in Europe wherein oil is sprayed ontophot nickel-containing bodies and thereby converted into combustiblegas haviugheating values in the oil gas range. A consideration of thepublished data concerning this process shows, however, that theeiiciencies obtained by `this process in producing oil gas are very low,from over 50% to 85% of the combined carbon content of the oil'appearingas the low B. t. u. water gas reaction product of carbon withsteam andas carbon, tar, Yand the like. "Ihat is to say, the higher B. t. u. gas"produced, while consisting largely of oil gas with a minor amountofwater gas, is made at the expense of producing a large amount of carbon,tar, and the like; whereas the lower B.V t. u. gas is preponderantlywater gas, and the production thereof is still accompanied by the,production of large amounts of carbon, tar, and the like. Moreover, thegas-generating capacity of this process is also krelatively low.

It is the principal object of the present invention to provide a novelcyclic catalytic method for producing from a liquid petroleumhydrocarbon a combustible gas consisting mainly of oil gas by which areprovided couversion eliiciencies substantially higher than thoseheretofore obtainable.

It is another object of the present invention to provide a novel cycliccatalytic method for producing from liquid petroleum hydrocarbons acombustible gas consisting mainly of oil gas which process not onlyprovides conversion efficiencies substantially higher than heretoforeobtainable, but also accomplishes these results under high capacityoperation.

content, and lower for oils of high Conradson carbon or Vhigh sulfur.The fact that about half or more of the combined carbon of the oil isnot converted to'gas, but rather to free carbon, tar, and the like, notonly means poor efficiency, but also the production of materials thatpresent handling problems. The production of carbon Still another objectof the present invention is to provide a method for producing acombustible gas consisting mainly of oil gas not only at high conversioneiliciencies under high capacity operation but also with minimum plantinvestment costs per unit Yof gas volume produced.

'aisselles f 'Still another object of the present invention is toprovide a method by which the foregoing objects may be realized by thecatalytic treatment of vaporized liquid petroleum-'hydrocarbonsYincluding petroleumoils containing Yhigh contents of Conradson carbonand sulfur, in spite of the fact that the catalyst employed is sensitiveboth to carbon deposition'and to sulfur poisoning.

Other objects Vwill become apparent from the 'following specificationand the claims.

One might think that the production of oil gas by the treatment of ahydrocarbon with a catalyst would merely involve subjecting thehydrocarbon to the catalyst for a shorter contact time than is the caseincomplete reforming. Following this theory, an attempt was made toproduce such "an oil gas fromlight oil by reducing the thickness Vof'catalyst zonethrough which the oil passed. However,.failure resulted.Heavy vcarbon deposition'and penetration .during the gas-making periodresultedin ageneral loss of catalyst activity. lo the extent that carbonisfdepositedlon the catalyst, catalyst effectiveness -in 'promotinghydrocarbon cracking reactions is reduced and the process approachesordinary thermal cracking fin nature. Attempts completely to removeexcessive deposits 'duringeach heating period resulted inexcessively/,high surface temperatures and spalling of the catalystleading to its rapid destruction. l

It has been found, however, that it is possible catalytically to crackor split lliquid petroleum hydrocarbons, including heavy oils, into oilgas. even a high B. t. u. oil gas, Awith unusually high conversionefficiencies, substantially higher, in fact, than that heretoforeobtainable in conventional oil gas processes. While a minor amount ofwater gas is also produced in the process, the present inventionV is-primarily concerned with the efficient conversion ofiliquid petroleumhydrocarbons to oil gas. Moreover, the production of a combustible gasrich in oil gas at vrhigh conversion efficiencies can be achieved withmaximum production capacity with maintenance of optimum catalystactivity. The foregoing is accomplished by controlling certainconditions within fixed limits and by observing definite relationshipsbetween certain of these controlled conditions. These conditionsinclude: hydrocarbon feed rate, concentration of available nickel on thecatalyst,mass of the catalyst body relative to itssurface area, andtemperature. The success of the processl is governed by the catalyticeffectiveness `of the nickel. `This depends not only upon properdistributionof the cracking load with respect Ato catalyst surface,areaV and availablenickel concentration soY that carbon and sulfurdeposition is not concentrated unduly at. any limited portion of 1 thecatalyst zone, but also uponY the way in which the heating-regenerationportionY of the cycle is conducted 'so that regeneration of the catalystby substantially complete elimination of carbon `and sulfur during thiskportion of each cycle is possible while rnaintainingA thetemperaturesthroughout the catalyst zone withinclosely controlled limits.

The process of the presentrinvention, therefore, is a cyclic procedure,that is, it involves` alternatingV heatingregeneration andgas-makingsteps, utilizing a hot fixed zoneyof catalyst comprisingnickel-containing refractory bodies having a mass between about 95 andabout 1000 lb. per 100 square `feet of surface and vhaving nickelavailable at the surface thereof in aconcentration, in the outer V/gginch` of catalyst body, of between about 1.4 and about 4 lbs. per 100square feet of surface, and comprises during'the gas-making portion ofthe cycle, passing a vaporized liquid petroleumhydrocarbon and steaminto said zone of catalyst at a rate'withj respect to the area ofcatalyst `surface and concentration of available nickel in. accordance.with the equation;

Hydrocarbon feed rate (lbl carbon/hour) Catalystleur'faee (ft.2). Y

Ni concentration (lim/100 ft..2 surface)` whereinX is between vabout 2and about 6, preferably between about 3 and about 5, the temperaturegradient in said catalyst zone during the passage of hydrocarbonthereinto being no greater than about 100 F.; then, before thetemperature'ofthe catalyst zone drops appreciably more than about 10.0F., discontinuing the flow of hydrocarbon, and reheating andregenerating the catalyst zone.

The process of the present invention will be more readily understoodVfrom a consideration of the drawing in which Figure l is a sideelevational view, partly in section, of one form of apparatus in whichthe present process may bejcarried out.

By controlling vthe stated conditions and observing relationshipsbetween certain yof them as discussed above,`

liquid petroleum hydrocarbons can readily be converted into combustiblevgas.consisting largely'of oil gas and having heating values-rangingfrom about 70() B. t. u. to about 1200 B. t. u. (N2 free basis).,Moreoven this gasification can be accomplished at an unusually highconversion eciency, thatis to say, proportion of carbon in the feedstock appearing'in the gas. In fact, by the present process conversionefficiencies of from 70% to 85% are easily obtained, and these are to becontrasted to efficiencies inthe. order Yof 40-50% achieved byconventional oil gas processes in the ,same B. t. u. range. Sucheiciencies Yare also obtained -at high operating capacities, and theprocess can Vbe operated in equipment involving minimum investment costper unit of gas volume produced since 4the equipment is simple and maybe readily constructed of conventional gas-rnaking equipment withappropriatemodications as will be apparent fromthe drawing. Y

A valuable feature of the process is that it can be utilized in the:treatment of any normally liquid petroleum Vhydrocarbon ranging fromlight distillates to heavy oils of high Conradson carbon and sulfurcontents. Examples of ,liquid petroleum hydrocarbons which may betreated are naphtha,.gasoline, kerosene, diesel oil, bunker C oil, heavyresiduum oil, and the like.

The catalyst employed in accordance with the process of the presentVinvention comprises discrete bodies of refractory `material havingVnickel available at least at the surface thereof. The nickel may merelybe dispersed at the, surface of suitable refractory bodies, such asalumina, aluminum silicate,-,mag'nesia,vor the like, or it may bedistributed throughout the refractory `body' so long as it is alsopresentv atthe surface, In the preparation of a preferred typeofcatalyst, preformed refractory bodies, such v:as Alundum, YareVimpregnated with a nickel vsalt and thereafter'the :impregnated shapes`are calcined to form the oxide` of the nickel whichV is subsequentlyreduced. The catalyst, as stated, will be in the form of discretebodies,such as spheres, cubes, cylinders, pellets, pebbles, andthe like. vThecatalyst bodies will also be relatively dense,l that-fis, they will havea porosity no greater than about 35%, and preferably of from about l0`to about 20%.

I t has been foundthat vthe reactions taking place in the present'process `are confined to a very thin surface layer of the Ycatalystbody.- At Ythe relatively high space velocities employed, the effectivenickelhas been found to-be 'that present'infthe outer 1/32 of an inch ofthe catalyst body. VTheconcentration of nickel in this outer layerhasvbeen found tojbe an important factor. With too little nickel thebodyapproaches a non-catalytic refractory body resulting primarily inthermal cracking as in conventional oil gas processes, and thegas-making operationgbecomes difficult to control. Y It has been foundthat .theaniount of nickelin `the outer 1;@2 of an inch of theQatalystboclies should .be at least L4 lbsper 10U square feet ofcatalyst surface., `Preferablythe amount of nickel Vonthis ',basisisbetween `about 2 and aboutl 3 lbs perf .100. -sqruare ,feet of catalystsurface. On the of the catalyst zone.

2,828, teeother hand, if the concentrationl of nickel at the surface' istoo high, it has been found that the reactionsare con# centrated in arelatively thin portion of the catalyst zone. and unduly large amountsof carbon become deposited per unit surface of catalyst body. Thiscarbon deposition not only reduces theclfectiveness of the nickel duringthe ygas-making portion of the cycle thereby causing the body toapproach in function a non-catalytic refractory body and therebypromoting thermal cracking, but also gives rise to difficulty in itsremoval since long burning times or excessive temperatures would berequired which in turn would result in high local surface temperaturesand spalling. Amounts of nickel much in excess of about 4 lbs. per 100square feet of catalyst surface may give rise to the above discussedcarbon deposition problem. Within the above-mentioned limits,combinations of catalyst bodies having different concentrations ofavailable nickel may be employed.

Another important factor in accordance with the process of the presentinvention is the mass of the catalyst bodies in relation to the surfacepresented thereby. Temperature variations at the catalyst surface duringthe gasmaking portion of the cycle must be maintained at a minimum.During the gas-making portion of the cycle, heat is being abstractedfrom the catalyst bodies. The greater the mass of catalyst body inrelation to the surface area presented thereby, that is to say thegreater the weight of the catalyst per unit surface area, the less rapidis the drop in temperature at the catalyst surface during the gas-makingportion of the cycle. Each catalyst body, therefore, must serve as areservoir for stored heat which can be conducted to the catalyst surfaceduring the gasmaking reactions. Hence, the catalyst size must not beless than that required to insure sufficient heat storage to prevent toorapid a temperature drop at the catalyst surface. On the other hand, toolarge a catalyst body size results in excessive mass and volume per unitof catalyst surface and therefore, ineflicient utilization of catalystspace. It has been found that the mass of each of the catalyst bodiesshould be such as to present between about 95 and about 1000 lbs. per100 square feet of catalyst surface area. In terms of spherically shapedcatalyst bodies comprising Alundum of less than 35% porosity as thecarrier, for example, this would mean diameters of between 1/2 inch andabout 3 inches.

The exact size of the catalyst bodies may depend to some extent upon thenature of the liquid petroleum hydrocarbon being treated. It has beenfound that with the heavier petroleum hydrocarbons larger sized catalystbodies are desirable. While the larger sized catalyst bodies can also beused in the treatment of the lighter liquid petroleum hydrocarbons aswell as the heavier hydrocarbons, the converse is not generally truesince the smaller sized catalyst bodies are not as effective with theheavier hydrocarbons as are the larger sized catalyst bodies. Forheavier hydrocarbons, such as diesel oil, bunker C oil, and the like, itis preferred that the mass of the catalyst be such as topresent betweenabout 750 and about 1000 lbs. per 100 square feet of catalyst surfacearea.

Combinations of catalyst bodies having different masses or sizes may beemployed. However, extreme differences in catalyst body sizes such aswould cause close packing and -excessive resistance to gas ow should beavoided. The void space between the catalyst bodies preferablyrepresents about 3S to 40% of the volume This also prevents excessiverates of mass transfer between the catalyst surface and the reactanthydrocarbon vapors and consequent localization of carbon deposition.

In laccordance with the process lof the present invention, the rate offlow of the petroleum hydrocarbon into the catalyst zone is controlledwith respect to the nature of the nickel catalyst employed. The absoluteow rate of the hydrocarbon may, of course, vary widely dependcycle.

ing upon thesize "of 'the gas-producing equipment. -The'` importantfactor, however, insofar as the present process is concerned, is therelationship between the How rate of the hydrocarbon reactant and thecatalyst mass, surface and available nickel. Since the mass of catalystbody and the nickel concentration have been related to surface thisrelationship is most easily expressed as a function of hydrocarbon feedrate and total available nickel. Since the nature of the petroleumhydrocarbon will vary as to molecular weight, carbon-to-hydrogen ratio,and the like, it is most convenient to express the flow rate thereof interms of pounds per hour of carbon in the hydrocarbon employed. It hasbeen found that, in order to produce a gas having a heating value in theoil gas range at the conversion eiciencies referred to above, it isnecessary that the feed rate of petroleum hydrocarbon be so controlled.with respect to the available nickel as to provide a value of betweenabout 2 and about 6, preferably between about 3 and about 5, for thefollowing ratio, the weight of nickel being that in the outer )g2 inchof the catalyst body:

Hydrocarbon feed rate (lb. carbon/hour) Catalyst surface (ft.2) `Niconcentraticmlb/ 100 ft. surface) Process steam is also employed withthe hydrocarbon reactant during the gas-making portion of the cycle toserve as diluent and to aid in conducting heat to the vaporizedhydrocarbon, and for such water gas reaction as may be desired. Theamount of steam employed will generally not be less than about .8 lb.per pound of carbon in the hydrocarbon reactant. While the proportion ofsteam may be well above this figure, such as up to 2 to 3 lbs. normallyit is not necessary to employ over about 1 lb. per pound of carbon inthe hydrocarbon. Process air may also be employed during the gas-makingportion of the cycle when a higher gravity gas is desired. Such use ofair also helps to reduce temperature swing by combustion during thegas-making step.

The foregoing discussion has assumed that the catalyst bodies aresubstantially completely effective; that is to say, that the catalystbodies are substantially completely free of carbon and sulfur during theinitiation of the gasmaking portion of each cycle. In other words, it isessential, in accordance with the process of the present invention, thatthe catalyst be regenerated during each The portion of the cyclenormally devoted to re- -storing heat in the gas-making zone therefore,has a twofold function in the present process: (1) to reheat thecatalyst zone, and (2) to regenerate the catalyst, and this portion ofthe cycle will be referred to herein as the heating-regeneration portionof the cycle as distinguished from the other main portion of the cycle,namely the gas-making portion.

To reheat in part the catalyst zone, hot heating gases are required andthese may be provided by burning a fuel and passing the resulting hotproducts of combustion through the catalyst zone. Part of the reheatingof the catalyst zone is also accomplished by the combustion of thecarbon during regeneration as discussed more fully hereinafter. Aportion of the reheating is also accomplished, in accordance with thepresent process, by a catalyst oxidation-reduction and combustionsequence also more fully discussed hereinafter.

The regeneration of the catalyst requires oxidizing conditions so thatcarbon and any sulfur doposited on the catalyst during the gas-makingportion of the cycle, may be burned and removed as gaseous oxides. Theprocess will therefore, involve, sometime during theheating-regeneration portion of the cycle, the passage of free oxygenthrough the catalyst zone in an amount sufficient toy oxidize at leastsubstantially completely the carbon and any v excess air. so that thehot products of combustion flowingv message* through ther-catalyst zonewill contain free oxygen-: Oni ther-other: hand-2 air by itselflmay-She,- and preferablyA is,-`

passed through -the het Ycatalyst Zone;v especially-2 v'when theVhydroc'aibon'react-'ant contains-over"l .02%- ofv sulfur.v

In this latterconnection;V it is particularly advantageousto pass freeair-through-the catalystzone-atV the-beginning oftheheating-regeneration portionv ofthe-cycle.A The rapid and? completeremovalof--sulfurirequires'not onlyv relatively high'temperatures,`butalso --a relativelyhigh oxygen concentration,- such-as lin ain- TheIpassagel of ,f ree air -throughthecatalyst --zone- -qui'ckl-y burnsyoilC fcarbon producinghigh temperatures.- Thus, bypassngair through thef catalyst/zoneat-the beginning ofthe heatingregeneration portion-ofthecycle,- thehigh` temperatures and' oxygen concentrationrequired-f forYremoval Aof the last tracesofthe -sulfur are-readily-provided.Byanalysing the -gasesissuingfrom the=catalystzone at' this timev orlater inthe heating-regeneration portion-tof the cycleA of sulfurv isconducted by .passing a .sample of the gasesVA through a filter paperimpregnated with barium hydroxide, starch, potassium iodate,and-potassium'iodide in accordance withthe test set forth in MethodvlforV the Determination of Toxic Gases in Industry, Leaflet No. 3,Sulphur Dioxide, published by the British Department of Scientic andIndustrial Research, 193 8.

As stated previously, oneof the important factors of control in theprocess of the present invention is the main-- tenance of controlledtemperature-variations during the gas-making portion of the cycle. Thatis to say, temperature swing and gradient during the gas-making portionof the cycle must be maintained at-a minimum. By temperature swing ismeant herein-the changes inthe temperature at any given spot inthecatalyst zone throughout the gas-making portion of the cycle, whereastemperature gradient as used herein refers to the difference between themean temperatures of the entran-cehalf and of the exit half of thecatalyst zone at any given time during the gas-making portion of thecycle. Since the observed temperature swing may vary depending uponthe-particular means and method employed Ain its measurement, theternperature swing referred to herein is based on measurements using athermocouple in a stainlesssteel shield imbedded laterally about onefoot in the catalystzone, and located within the central 80% ofthecatalyst zone. Y

In accordance with the process of the present invention both temperaturegradient and temperature swing will not exceed about 100 F. In otherwords, for any given hydrocarbon treated in accordance with the presentinven.

tion, there is a relatively narrow temperature band or range withinwhich the desirable high B. t. u. gas-making reactions are promoted andside reactions, such as, the water gas reaction, carbon deposition,andthe like, are held at a minimum. The exact limits of this band-orrange will depend on the particular petroleum hydrocarbon being treated,and may fallanywhere between about 1400" F. and l700 F. The selection ofthe specific range for any particular petroleum hydrocarbon will presentno problem to those skilled in the gas-making art as long as theforegoing considerations concerning temperature swing and gradient areobserved.

Temperature swing is controlled by providing the proper mass of thecatalyst bodies and by proper distribution of the cracking reactionsover the surface. thereof as discussedA above, and by limiting theduration ofthe gas-making portion of each cycle. lu this latterconnection, since the gas-making reactions abstractA heat from thecatalyst zone,.the .temperatureldropzthereinwill.

dependupon.thsfquantity ofY 'reactant gasied per cycle.V Generally, at*the rates of fiowdnecessary to provide high t capacities-fthe completecycle of 'the present process willl be limitedto about 1:5;3' minutes,the gas-making portion of fthe, cycle taking up .3 5455 of that time.

Temperature gradientiscontrolled primarily by a heating procedureof.theztype disclosed and claimed'in copending application of Harold V..Erickson vand Francis W. Hartzel, Serial No. 279,934, tiled April 1,1952, andnow maturedziritolUS: Patent Nail-.759,805 issued on August 2l,i956. As explainedimthat application,A the passage of hot productsVcfs-,combustion through' a stationary catalystV zone results Iinratemperature gradient over the.. zone whereinzth'e temperatures -at theportion of the zone whereinl the :hotrg'ases enterfare Lsubstantialiyhigher.r than It has been tound. however, that if the `catalystcomprises an easily oxidizable z metal, such` as nickel, andgif; whilelthe catalyst is hot, air` the temperatures ingthe ,exitportion or otheroxygen-containing gas 4is passed throughthe catalystzonel tooxidizefthe`nickel following which a reducing gas is passedA throughl ther-catalystzone reducing the oxidized nickel to the elemental metal state, thetemperature gradient through the catalyst; zone is reversed. In otherwords, by this latter system of, heating, the exit portion ofthecatalystzone has a higher-temperature than that of The oxidation of thenickel, of course, generates heat; 'Whilethe reduction of the oxidizednickel back` tometallicform absorbs theoretically the same amount ofbean-this reduction is accompanied the entrance portion.

simultaneously by the oxidation of the reducing gas employed to reducethe catalyst goxirde.V combustion) Y generates anadditional quantity ofheat. Hence,V the net result ofthis catalyst oxidation-catalystreduction-combustion sequence is the generation of heat which is storedin the catalyst zone providing the increasing-temperature gradientreferred to above. To provide relatively uniform temperature conditionsthroughout the catalyst zon e,-there fore,the heating-regenerationportion of the cycle-may comprise a combination of these two types ofheating;rnamely,;the passage of hot combustion products through-the-catalyst zone and they oxidationreduction-combustion sequence referred`to. By controlling Athe proportions of each'type of heating means,t-ogether with the-heatliberated-by the burning o'ic of depositedcarbon, the temperature gradient in the catalyst zone can readily bemaintained below about 100 F.

The catalyst-oxidation phase of the above-describedl catalyst-oxidation,y catalyst-reduction, combustion sequence may take place at the` sametime hot combustion productsare--passedthrough the catalyst zone tostore heat therein. in this case, the hot combustion products willcontain free oxygen provided, for example, by burning the fuelv in thepresence of excess air. The

catalyst-oxidation phase of the described sequence -rnay also beaccomplished at a time during the heating-regeneration portionof thecycle other than the time when hot combustion products are passedthrough the catalyst zone as by the passage-cf free air through thecatalyst zone. In anyfevent, 4surieient free oxygen will be passedthrough the catalyst Zone sometime during the heatingregenerationpo-rt-ionof the cycle to substantially completely burn-oit the carbonand any sulfur deposited in the catalyst zone duringthe gas-makingportion of the ber,l lined, with; refractory material 2,. servingkas are-- fractory-liped; path-for confining the catalyst zone.

Chambergl maybetor example, .the-superheater of a,-A`converational,rvateresas` Seta/itil..Yarmor;iatesmodifcation,-`

This oxidation (or,

as is 'obvious from the drawing. 3 represents a refrctory-lined chamberthe bottom of whichV is in fluid flow communication with the bottom ofchamber 1. Chamber 3, which may be the carburetter of a conventionalcarburetted water gas set, contains combustion zone 4 wherein fluid fuelis burned to provide hot gases for internally heating the set includingthe refractory material and catalyst zone therein. The zone of catalystin the form of discrete bodies is represented by 5, and is supported asby frebrick arch 6. One or more courses of irebrick 16 arranged infamiliar checkerwork pattern, or other heat-accumulating refractorybodies, maybe disposed between the supporting arch 6 and catalyst zone 5to serve as additional heat storage'material. Such'additional heatstorage material will be referred to herein as heat storage zone 16. Toprevent the catalyst bodies from falling down through the arches, orheat storage zone 16 if used, the catalyst mass may rest directly on aheavy metal screen (not shown) or on a layer of perforated refractorybricks or tile (not shown).

-Numerals 7 and S-represent, respectively, the air and Huid fuel supplymeans for combustion to provide hot gases for heating the apparatus, and9 represents the stack valve through which the waste heating gases maybe discharged to the atmosphere, or to a waste heat boiler (not shown),before being discharged to the atmosphere. Some or all of theregeneration air and air used in the discribed catalystoxidation-reduction-combustion sequence may also be admitted throughconduit 7. As discussed above, it may be desirable to pass air inaddition to the hydrocarbon and steam through the path during thegas-making portion of the cycle, and some or al1 of such process air maybe admitted through conduit 7. The conduit for the liquid petroleumhydrocarbon reactant for introduction into the path is represented by10, and a conduit for process steam at 11. Suitable preheating means(not shown) for the petroleum hydrocarbon reactant may be provided toinsure its vaporization in the path although it will be realized that aportion or all of the heat required for vaporization thereof may besupplied by the heat stored in the refractory material or catalystitself. A conduit, 12, may also be provided for admitting some or all ofthe process air or air used during regeneration of the catalyst and inthe catalyst-oxidation phase of the describedoxidation-reduction-sequence. 13 represents the conduit through whichproduct gas leaves the path, passing through wash box 14 to storage byway of valved conduit 15. In accordance with known gas practice, thegases leaving the path for storage may pass through a waste heat boiler(not shown) before reaching the wash box. The flow of the respectivematerials into and from the set through vision of a heat storage zonebetween the combustion Vof the high temperatures adjacent the combustionzone required for rapid igntion and uniform combustion of the fluid fuelduring the heating step of the cycle.

The operation of this .process is, as stated, cyclic, and the procedurecomprises a heating-regeneration period during at least a portion ofwhich air and fluid fuel are admitted through connections 7 and 3,respectively, combustion taking place in combustion zone 4. The hotcombustion-gases are passed through the confined refractory lined pathof chamber 1, storing heat in the lin ing, 2, and through the catalystzone and its supporting arches storing heat therein, and may then bedischarged through stack valve 9; When a heat storagetzone, such as 16isinterposed between the catalyst bed and its supporting arches, the hotgases will also pass therethrough storing heat therein. The hotcombustion gases also store heat in the lining of the combustion zoneandin the fluid Way between the combustion zone and the path of charnber1, and when a primary heat storage zone, such as 17, isemployed, thehot' gases will also pass therethrough storing h eat therein.

As stated, air 'itself is preferably passed through the catalyst to burnoff carbon and sulfur deposited on the catalyst. This is mostadvantageously done at the early part of the heating-regenerationperiod, just before fuel is admitted to the combustion zone. The air forthis purpose may be admitted through conduit 7 and/ or through conduit12.

For the initial step of the described catalystoxidationreduction-combustion sequence, oxidizing conditionsl are alsorequired, and air for this purpose may be admitted through conduit 7and( or through conduit 12. The reduction-combustion portion of thissequence requires reducing conditions, that is, an oxidizable reducinggas must be passed through the catalyst zone to reduce thecatalyst'metal oxide to metallic state and be in turn burned. For thispurpose a producer gas, made by burning, in 4, fuel in the presence ofinsuilicient air .to support complete combustion, may be passed throughcatalyst zone 5. However, this portion of the stated sequence mayactually be, and preferably is, conducted during the early stages of thegas-making period when the rst increments of hydrocarbon reactant areadmitted to the catalyst zone. Sufficient of this material will becomeconverted to reducing gases, particularly hydrogen, Ito cause thereduction' of the catalyst metal oxide to elemental form with thesimultaneous combustion of the the described conduit means is controlledby suitable Y valves as shown.

A primary heat storage zone 17 for preheating a portion or all of theregeneration, catalyst-oxidizing or process air or process air orprocess steam may be, and preferably is provided as shown in thedrawing. Heat storage zone 17 comprises heat accumulating refractorybodies such as rebrick arranged in familiar checkerwork pattern, asshown, or randomly arranged pieces of refractory material, or acombination of both. The heat storage material may be supported as byrebrick arches 18. Heat storage zone 16, disposed, in accordance withthe preferred embodiment, between the arch and the catalyst zone, may beprovided as discussedabove, and this may be constructed as described inconnection with heat storage zone 17.

Where a primary heat storage zone, such as 17, is employed, a portion orall of the process steam may be introduced prior thereto as throughconduit 19. Usually, it will be found advantageous to introduce at leastpart of the process steam or air, or both, into the combustion zone asthrough conduits 19 and/or 7 to prevent excessive accumulation of heatat that point. The pro reducing gas by virtue of the oxygen of thenickel oxide. During this step, the gases produced may, if desired, bevented to the atmosphere through stack valve 9.

After the path is at operating temperature and the catalyst is at leastsubstantially free of carbon and sulfur as may be determined, forexample, by analyzing samples of the gases leaving the catalyst zone,the gas-making portion of the cycle is commenced. Connection 10 isopened to admit the liquidrpetroleum hydrocarbon reactant. At the sametime process steam may be admitted through connections 11 and/or 19 andany process air may be admitted through connections 12 and/or 7. Theliquid hydrocarbon, if not already vaporized upon admission to the path,becomes vaporized by virtue of high temperatures therein. Throughcontact with and radiation from the hot refractory material of thelining and arches supporting the catalyst zone the hydrocarbon, and theprocess steam, and process air if used, become heated substantially toreaction temperature.

When a portion or all of the process steam and/or air is admitted to thecombustion zone, it becomes preheated in lpart by contact with andradiation from the hot lrefractory-lining and any other heat storagematerial such as heat storage zone i 17 and its supporting arches,preceding the path of cham? message@ the gas-making portion of" thecycle, stack 9 isclosed.; Y In passing through the catalyst'zone 5,.thehydro-r carbon reactant iirst becomes broken down into stablehydrocarbon gases such as methane,..ethylene,'propylene and the like,and into hydrogen and carbon.. Some hydrogen and carbon `monoxide arealso formed by re.

action between this carbon and process. steam.' The product thus issuingfrom the` catalyst zone is 1n the form of a stable,.xed combustible gascomprising gaseous hydrocarbons, hydrogen and .carbon monoxide. The gasyisled off through conduit 13 into wash box 14 and, by way of valvedconduit 15, ,to storage.

Beforethe temperature of the catalyst zone hasdropped more than about100 F. as discussed previously herein, the admission of hydrocarbonreactant through conduit 10, and of process'steam through conduit 11and/m19, and any process air through conduit 12 and/or 7 is stopped,andthe set again heated and catalyst zone re.

generated as described.

It will be realized that, in accordance with commonY gas-makingpractice, steam purges may be, and prefer-. ably are, made between theheating and gas-generating portions ofthe cycle, or between thegas-generating and heating-regeneration portions of the cycle, or both."These purges, asknown to those familiar with the gas`v making art, serveto clear the system of undesirable gases which may contaminate thegenerated VgasV or serve to force residual desirable gases to storage.Such purges: may be conducted as by admitting steam through conduit 19,.

While the drawing in Figure 1 illustrates a ,two-shell.

set, it will be understood that a single chamberv or three chambers maybe employed, and the process carried out following the same generalprinciples describedabove.;

Likewise, while the catalyst zone is illustrated as a single layer ormass, itwill be realized that the catalyst zone may be in the'form oftwo or more separate layers i11-V cluding layers in separate shells.

It has also been found that the .provision of` a small amount of nickelon the exposed surfaces of the heat storage refractory material withwhich the hydrocarbon reactant will come into contact after it isadmitted'to the gas-making set and before, it reaches the catalyst zone,such as the refractory lining 2 above conduit 10 and be,-A

low arch 6, and the surfaces of arch 6 and heatfstorage. f zone 16, willprevent thermal cracking of the` hydrocarbon inl spite of the fact thatthe temperature ofsuchf heat storage refractory. material may be abovethethermall vided on suchexposed surfaces.

This nickel: film, the provision of which is-v disclosed i and claimedin copending application Serial Number cracking temperature ofthehydrocarbonp Thus,:in;ac. t cordance Vwith this embodiment, a film of;nickel is pro- 491,985, iiled March 3,1955, by Charles G. Milbourne,

the surface. The overall result is the provision of a relatively uniformdeposit of finely-divided nickel on the surface on the refractorymaterial. In connection with the foregoing, a nickel salt such as nickelammonium chloride, nickel nitrate, nickel ammonium sulfate, nickelchloride,A nickely sulfate, and the like, may lne-employed.

A, concentration of about' 4 to 6% nickel,` by weight,`

based on .the-.outer of an Vinch of surface, is provided.

Thearnount .of nickel'deposited on. the surfacemayvary A from v.theaboge-statedfamounta-and may. be, as,.lt .vv..,.asv

During application, Ythe However, upon drying there i will be sometendency for lthe solution to migrate towardv surface.;Amcunts-.aboveabout :8 %l. ofithefs'ame basis generally. dov notprovidecorresponding increases yin ze'tecfAV tiveness and hence, willgenerally not be employed.; 'The nickel may, of course,"penetrate to.anVextent greater than'.-

1/2 ofaanzinch, however, since. the effect is fpriinarilyl'aIysurfaceelect, only.: the. outer 1/32 inchmay. be. reckoned Y with.'nConveniently, the reduction ofithe salt,.and, ini fact, both drying. andreduction, can Atakeiplace.during.; one heating operation, suchvasduring. the normal starting.

Luptofftherunit `where 4temperatures above 750` ,Fl are employed.

The, :process of the present "invention will be more clearly-tunderstoodfrom .a consideration of the following specic-.exampleszwhich areqgivenfor. the. purposeoti: illustration onlyand tare not intended to limitthe.. scopef: off'the .invention in. any way.

EXAMPLES I-IV' In these examples icorrrmercialv size requipmentjof.Vthe: design shown generally inthe drawing is employed com- -pnfisingv aYcombustion chamber` and an upright, 10 ft. LD., refractory-linedshell.- The catalyst zone is disposed 1 as a layer across the shell andsupported by refractoryY arches.` Two Vminute cycles ,are employed,``the-'gas- :rnaking portion taking up '5S-42% of the cycle.Followingeachgas-making run isa steam purge takingup 1-2% of the cycle,then a blast of-air alone taking up l-2% of"A the cycle. Following this,-fuel is burned in the presence. 1 of excess -air land the resultingoxygen-containing prod- .ucts'of combustion are passed through thecatalyst zone..

This takes up 45-51v% Vof the cycle. At the end of this step the nickelexists in oxidized: form. Following briefV air-and-steam purges, whichtake up 3-l1% .and 1-3%. respectively of the cycle, the gas-making runis repeated.v The iirstincrements of hydrocarbon reactant whichbreak 1down to hydrogen are relied upon to reduce the oxidized nickel Vtoelemental form.

Example I In `this example the catalyst, in two dilerent sizes, is'arrangedin two superposed layers. One layer, 3 inches deep, consists ofpebbles having a diameter of .5 inch, and the other layer, 14% inchesdeep, consists Vof pebbles'. 1 .inchin diameter. In both catalysts sizesthe amount of l nickel. in the outer 1/32 inch of surface is 1.5 lbs.per 10() square` feetof surface area, and the mass of the combinedlcatalyst is 165.5 lbs. per square feet surface area.

Duringthegas-makingjperiod, kerosene is vaporized and -passedthrough thecatalyst zone at a rate corresponding` to 433 lbs.v carbon per hour per100 square yfeet of catalyst surface, or 283 lbs, carbon per hour perlb. of availableinickel (inthe outer-V32 inch layer).

The resulting gas has a heating Value of 838 B. t. u. (N2-free basis)vandv 77.2% of thecarbon in the kerosene appearsinthe-gas.. 63.5% asAgaseous. hydrocarbons and: 13.5% as carbon monoxide .plus hydrogen. Y

Example Il,

Inthisjexample the catalyst .consists of 1 inch spheres, and the .amountof nickel in the outer- 1/{32 inch of surface is.2. 77 lbs.` pelglOOsquareY .feet of surface. The depth of thecatalystzone Vis 15 inches,and the mass of catalyst is `195 lbs..perl.100 squarefeet. of surface. nDuring thegasf makingrun; kerosene is .vaporized and passed through thecatalyst zoneat a rate correspondingfto 630 lbs. of carbonperhourTper100fsquarefeet ofcatalyst surfaces, or 215 lbs. carbon per hour perlb. of available nickel.

The resulting-gas-hasfa heating Value of 740 B. t. u. (Ng freebasis),and` 72,7% of the carbonin the kerosene appears r'in the gals, ,54.2% asgaseous hydrocarbons and lf3-.5 as whoa-monoxide. plusA hydrogen In,this examplcgthe .catalystzoneiis vv.made .up .ot l inch about 2%',by'wcight, based ron the` oute'rfl-g inch of *spheres havingi1-64 lbs.of nickel perl 100 square'fet'f 2,sas,1se

. 13 surface area in the outer 3/32 inch. Thebed depth'is 15 inches, andthe mass of catalyst is 195 lbs. per 100 square feet of surface.

- During the gas-making run, kerosene is vaporized and passed throughthe catalyst zone at a rate corresponding to 490 lbs. carbon per hourper 100 square Afeet of surface, or 280 lbs. carbon per hour per lb. ofavailable nickel.

The resulting gas has a heating kvalue of 734 B. t..u. (N2 free basis)and 73.2% of the carbon in the kerosene appears in the gas, 54.6% asgaseous hydrocarbons and 18.6 as carbon monoxide plus hydrogen.

Example IV In this example the catalyst zone consists of 1 inch spheresat a depth of 9 inches. The catalyst bodies contain 2.77 lbs. of nickelin the Outer 1/32 inch per 100 square feet of surface. The mass of thecatalyst is 195 lbs. per 100 square feet of surface.

During the gas-making run, kerosene is employed, being passed, invaporized form, through the catalyst zone at a rate corresponding to 834lbs. carbon per hour per 100 square feet of catalyst surface, or 284lbs. carbon per hour per 1b. of available nickel.

The resulting gas has a heating value of 705 B. t. u. (N2 free basis),and 71.2%of the carbon of the kerosene appears in the gas, 52% asgaseous hydrocarbons and 19.2% as carbon monoxide plus hydrogen.

EXAMPLES V-XI In these examples the catalyst is arranged in an uprightrefractory-lined shell having an inner diameter of 13 inches. Two minutecycles are employed, the gas-making portion taking up 40-50% of thecycle.

Example V In this example the catalyst bodies are in the form ofcylinders 2 inches in diameter and 2 inches in length. The catalystlzone is 66 inches in depth. The amount of nickel in the outer l@ inchof catalyst body is 1.41 lbs. per 100 square feet of surface, and themass of the catalyst bodies is 858 lbs. per 100 square feet.

During the gas-'making portion of the cycle, diesel oil is vaporized andpassed through the catalyst zone at a rate corresponding to 516 lbs.carbon per hour per 100 square feet of catalyst surface, or 366 lbs.carbon per hour per lb. of available nickel.

The resulting gas has a heating value of 842 B. t. u. (N2 free basis),and 74.1% of the carbon in the diesel oil appears in the gas, 62.7% asgaseous hydrocarbons and 11.4% as carbon monoxide plus hydrogen.

Example VI Example VII 'In this example the catalyst zone consists of 1inch spheres at a depth ofA 8 inches. The amount of available nickel'is1.4 lbs. per 100 square feet of surface, and the mass of catalyst is 192lbs. per 100 square feet of catalyst surface. v

During the gas-making portion of the cycle, kerosene is vaporized andpassed through the catalyst zone at a rate corresponding to 704 lbs.carbon per hour 100 square feet of catalyst surface, or 520 lbs. carbonper hour per lb. of available nickel.

The resulting gas has a heating value of 678 B. t. u. (N2 free basis),and 72.1% of the carbon in the kerosene ap- ExampleV VIVII In thisexample the catalyst zone consists of 1 inch spheres at a depth of 4.4inches. The catalyst bodies contain 2.8 lbs. of availablenickel per 100square feet of surface, and the mass of the catalyst is 200 lbs. per 100square feet of surface.

During the gas-making portion of the cycle, vaporized kerosene is passedthrough the catalyst zone at a rate corresponding to 1270 lbs. carbonper hour per 100 square feet of catalyst surface, or 425 lbs. carbon perhour per lb. of available nickel.

The resulting gas has a heating value of 664 B. t. u. (N2 free basis),and 77% of the carbon inthe kerosene appears in the gas, 53.4% asgaseous hydrocarbons and 23.6% as carbon monoxide plus hydrogen.

VExample IX In this example the catalyst zone consists of 1/2 inchspheres at a depth of 4.4 inches. The catalyst bodies contain 2.4 lbs.of available nickel per 100 square feet of surface, and the mass ofcatalyst is 97 lbs. per 100 square feet of surface.

During the gas-making portion of the cycle, gasoline is vaporized andpassed through the catalyst zone at a rate corresponding to 690 lbs.carbon per hour per 100 square feet of surface, or 290 lbs. carbon perhour per 1b. of available nickel.

The resulting gas has a heating value of 835 B. t. u. (N2 free basis),and 70.6% of the carbon in the gasoline appears in the gas, 53.5% asgaseous hydrocarbons and 17.1% as carbon monoxide plus hydrogen.

Example X This example is the same as Example IX except that thecatalyst zone depth is only 1.6 inches and the gasoline is passedthrough the catalyst zone at a rate corresponding to 612 lbs. carbon perhour per 100 square feet of catalyst surface, or 254 lbs. carbon perhour per lb. available nickel.

The resulting gas has a heating value of 692 B. t. u. (N2 free basis),and 78.2% of the carbon in the gasoline appears in the gas, 58.9% asgaseous hydrocarbons and 18.4% as carbon monoxide plus hydrogen.

Example XI This example is the same as Example IX except that thegasoline is passed through the catalyst zone at a rate corresponding to556 lbs. carbon per hour per 100 square feet of catalyst surface, or 232lbs. carbon per hour per lb. of available nickel.

The resulting gas has a heating value of 655 B. t. u. (N2 free basis),and 83.8% of the carbon of the gasoline appears in the gas, 59.4% asgaseous hydrocarbons and 24.4% as carbon monoxide plus hydrogen.

Modification is possible in the selection of the various conditions,factors and techniques followed and observed as well as in thecombinations thereof, without departing from the scope of the invention.

We claim:

1. The cyclic method for producing a combustible gas rich in oil gaswhich comprises, in one part of the cycle, passing a vaporized normallyliquid petroleum hydrocarbon and steam, at a ratio of between about 0.8and about 3 pounds of steam per pound of carbon in said hydrocarbon,into a hot stationary zone of catalyst having temperatures of al leastl400 F. at which high B. t.. u. gas-making reactions with the liquidpetroleum hydrocarbon selected are promoted and the water gas reactionand carbon deposition held at a minimum, having a temperature gradientrio greater than about 100 F. and comprising nickel-containingrefractory bodies having a mass between about and about 1000 pounds persquare feet of surface and a nickel concentration,

ensues iii-*the outer ginch of surfacerof between about 1.4 and about 4pounds per 100 square feet of surface, said hydrocarbon being passedinto said catalyst zone at a rate to give a value between about 2 andabout 6 for the ratio:

Hydrocarbon feed rate (lb. carbon/hour) Catalyst surface (ft2)XNiconcentration (lb/100 ft.2 surface) then, before the temperature inthe catalyst zone falls appreciably more than about 100 F. and below1400 F., discontinuing the flow of hydrocarbon and steam and reheatingthe catalyst zone and regenerating the same by burning therefrom carbonand sulfur deposited therein while maintaining a temperature gradientof, no greater than about 100 F.

2. The method of claim 1 wherein hot refractory sur carbon selected arepromoted and the water gasireaction and carbon deposition held at aminimum, having a temperature gradient no greater than about 100V F. andcomprising nickel-containing refractory bodiesV having a mass betweenabout 95 and about 1000 pounds-per. 100 square feet of surface and anickel concentration, in the outer 1,432 inch of surface, of betweenabout 2 and about 4 pounds per 100 square feet of surface, saidhydrocarbon being passed into said catalyst zone at a rate to give avalue between about 3 and about' for the ratio:

Hydrocarbon feed rate (lb. carbon/hour) Catalyst surface (ft2) XNiconcentration (lb/100 ft.2 surface) then, before the temperature in thecatalyst z onevfalls appreciably more than about 100 P. and below l400F., discontinuing the flowof hydrocarbon and steam; burning a fuel andpassing the resulting hot products of combustion through said catalystzone to store heat therein, passing free oxygen .into said catalyst.zoneto burn therefrom carbonfand Vsulfur deposited thereinV and'toVVoxidize nickelingsaid` :catalyst zone, and. then/.passing oxidizable gasintosaid catalystzonereducing.said oxidized nickel with the oxidation ofsaidfgasin. said catalyst zone by virtue :of the oxygen of said oxidizedznickel,

the proportions `of heat provided bysaid hot combustion,v

products, the combustion of the deposited .carbon and the saidnickel-oxidation, nickel-reductionand gas-oxi dizing sequence providinga temperature gradient. in `said catalyst zone of no greater than about100 F. f

4. The method ofl claim l wherein the concentration of nickel in theouter 5&2 inchof catalyst surface is between about 2 and about 3 lbs.per 100 square Yfeet of catalyst surface, and the hydrocarbon is passedinto the catalyst zone at a rateto give a value betweenabout 3 and about5 for said ratio.

5. rrhe cyclic method for producing acornbustible gas rich in oil gaswhich comprises, in' one partof the cycle;

passing'a'vaporizedpnorrnally liquid petroleum hydro-y carbon andsteam,Y at a ratio `of between vabont0.8 Vand about 3 poundsoffsteamper-.pound of'carbon'inY said hydrocarbon, intoa hot stationary zone of`catalyst having temperatures of atleast 2,1400a n. at; which highVA B.t'.. u. gasp-making reactions with-,the liquid` petroleum hydrocarbonselectedare .promoted and the `water .gas reaction and carbon.deposition held at' a minimum, having a tempegaturegradientnoggreaterwthan about 100 F. and

comprising nickel-containing refractory bodies having al mass betweenabout and about 1,000 pounds per 100 square feet of surface and nickelconcentration, in the outer M52 inch ofsurface, of between about 2 andabout 4 pounds per 100 square feet of surface, said hydrocar-V bon beingpassed vinto said catalyst zone at a rate to give a value Vbetween about3 and about 6 for the ratio:

Hydrocarbon feed rate (lb. carbon/ hour) Catalyst surface (ft2) Niconcentration (lb./l00 ft2 surface) passing airinto said catalyst zoneto burntherefrom car-v bon andsulfur deposited 'therein'and to oxidizenickel in said catalyst zone; burning a fuel and passing the resultinghotproducts of combustionthrough saidV catalyst zone to store heattherein, and then passing oxidizable gas into said catalyst zonereducing saidmoxridized nickel with the oxidation of said gas in saidVcatalyst zone by virtue of theoxygen of said oxidized nickel, theproportions of heat provided by said hot combustion products,thecombustion of the deposited carbon and the said nickel-oxidation,nickel-reduction and gas-oxidizing sequence'providing a temperaturegradient in said catalyst zone of no greater than about F. Y

6. The cyclic method for l"producinga combustible gas rich in oil gaswhich comprisesin one part of the cycle, passing vaporized normallyliquid petroleum hydrocarbonand steam, at a ratiopbetween about0.8 .andabout 3 pounds of steam perV pound of carbon in said hydrocarbon, into ahot stationary zone of catalyst havingv temperatures of at least 1400`F. at which high B. t. u. gas-making reactionsv withrthe liquidpetroleum hydrocarbon selectedare promoted andthe water gasl reactioncarbon being passed into` said catalyst zone -at arate to give a valuebetween about 3 and aboutv6 lfor the ratio: Hydrocarbon feed rate (lb.carbon/hour) Catalyst surface (ft2) Ni concentration (lb/100th2 surface)then, before the temperature insaid catalyst zone falls appreciably morethan about 100 F. and below 1400 F.; discontinuing the ow of hydrocarbonand steam; burning a fuel in the presence of excess air and passing theresulting hot oxygen-containing products of combustion through saidVcatalyst zone', the oxygenfin said products of combustion passingthrough said vcatalyst Zone being sucient to burn therefronrcarbon andsulfur deposited therein and to oxidize Vnickel in said catalystzone,and then .passing into said catalyst zone an oxidizable gasreducing said oxidized nickel with the oxidation of said gas' in thecatalyst zone by virtue of the oxygen of said oxidized nickel, theproportions of heat provided by said combustionproducts, the combustionof deposited carbon and said nickel-oxidation, nickel-reduction andgas-combustion sequence providing a temperature gradient over saidcatalyst zone of no greater thanabcut 100 F.

References Cited in the file of this patent UNITED STATES PATENTS2,042,998 Johnson Iunei2, 1936 2,071,286 Johnson et al. Feb. 16, 19372,524,840 Shapleigh Oct. 10, 1950 2,555,210 Wadill et al. May 29, 19512,665,979 Taussig Ian. 12, 1954 f

1. THE CYCLIC METHOD FOR PRODUCING A COMBUSTIBLE GAS RICH IN OIL GASWHICH COMPRISES, IN ONE PART OF THE CYCLE, PASSING A VAPORIZED NORMALLYLIQYID PETROLEUM HYDROCARBON AND STEAM, AT A RATIO OF BETWEEN ABOUT 0.8AND ABOUT 3 POUNDS OF STEAM PER POUND OF CARBON IN SAID HYDROCARBON,INTO A HOT STATIONARY ZONE OF CATALYST HAVING TEMPERATURE OF AT LEAST1400*F. AT WHICH HIGH B. T. U. GAS-MAKING REACTIONS WITH THE LIQUIDPETROLEUM HYDROCARBON SELECTED ARE PROMOTED AND THE WATER GAS REACTIONAND CARBON DEPOSITION HELD AT A MINIMUM, HAVING